I have a '99 600F4 that I have had about a year.It appears one of the owners before me was wheelie happy. There is even a little light underneath the bike, Im guessing this was for pictures.

My question/concern is that when I am on the front brakes and about to come to a stop, the bike will "dip" down as Im stopping a fair amount. Even if I just roll the bike forward a bit and hit the front brake it drops down like at least an inch or two then rebounds back up.
Would replacing the fork seals/oil help with this?

Also, about 6 months ago I had the carbs, plugand air filter cleaned because the bike was just running pig rich. Any time I put the clutch in and rev it to 5-6K+ black smoke would just plume. After I got it back there was very littleblack smoke when I would hammer the throttle. I was told that was just from carbon buildup and would go away with riding. I did pick up a couple extra miles/gallon due to the cleaning so I was happy. Here I am less than 6 months later and it is back to loading up on me and pouring black smoke when I nail the throttle. I have also lost a little bit of gas milage as well. The other day it was boiling hot and I was stuck in stop/go traffic. About every 10-15 mins I had to put in the clutch and nail it to clear it out. Otherwise it was sputtering like crazy on me, and I could have the throttle over half way (in 1st gear) and it was barely moving forward. Put in the clutch and nail the throttle and it would be fine after I smoked out the cars behind me lol. It has not done the sputtering thing since then, but it is still smoking anytime I really get on the throttle.
Do I need to clean the carbs again, or could I have a bad Diaphram/Jet?

I am hoping to head out to a CornerSpeed Class at the end of Sept but dont want to have any issues with the bike that might be unsafe. Any help with what could be going on is appreciated.

 

sounds to me the carbs are loading up with fuel, could be a couple of things first and foremost check all the vacum lines going to the tank, carb, and aircleaner. and if all that is ok could be the floats getting stuck and there in the carbs ... But i would start with my first idea just to see if theres a vacum leak somewhere...

What does your bike idle at?

 

Id say it idles anywhere from 11-1300. Some ams I have to throw the choke on it, but that is not that often or it sputters out on the 1st start of the day.

Thanks for the advice, I plan on cleaning the bike up this weekend, so Ill probably pull the tank and check out the lines while I am at it.

 

before you completly take the take off (or disconnect the hoses) grab some brake cleaner and spray all around the hoses while bike is running and see if the idles changes..

 

As far as the squishy front suspension... sounds like the guy adjusted the softness to be able to bounce it up easier and to make wheelie landings softer. Thats an easy fix, just get a flat head screw driver and turn the two preload adjusters on the triple tree a couple rotations. Make sure you do it evenly.

 

Dang... Didnt even think about that. I totally forgot that these things have the adjustable fronts from the factory. Im always in car mode, so Im still getting used to thinking about how bikes are setup! Ill definately take a look at that.

Way2fast4u, when I shoot that brake cleaner on there and (if) the idle changes, that will mean I have a nice little vacuum leak right. If it doesnt, should I just take apart the carbs and check everything that way? If the floats are actually getting stuck, will one look like its clocked differentl or something? Would cleaning fix it, or would I need to snag new floats from the Dealership? I just think it would be very odd to have to clean carbs that often would it not? Of course, this is considering the guy cleaned and tuned the bike properly in the 1st place...

The joys of carbs lol. My cars have all be EFI, so this is all a learning experience for me. I did find an awesome how to on here for the carb cleanup though .

Thanks for the input/ideas guys!

 

you said it right the Joy's of carburation!!

Well yes if you spray and idle changes then you have a leak, if nothing happens then i would start checking all the hoses that come in and out of the carb/tank to make sure there on and not disconneted.if all the above reveils nothing then time to get dirty. If you do take it apart might as well check all the jets to make sure there not clogged, and to determain if your float is bad is pretty easy just by sight ( this is how i usaully do my carbs on my race car..

And come to think about it more, do you no anyone that has a simalar bike, try switching ecu's.... Just a thought...

 

Cool man, thanks for the input. If worse comes to worse and I have to break down the carbs, you said you just eye the floats. Will the look cockeyed or something? Looking at the pics in the how too, it doesnt seem like there is much room for them to move around. Im guessing it will just look totally out of whack if one is bad right?

Ill try and play with the 3 tree in the am. Im guessing I will be turning clockwise to stiffin it? I have a couple manuals at home for the bike, so ill look through those as well.

 

unfortionately i had the same prob with my old r6 which was carb'd. it would sputter, idle, and act funny and thats why i got a fuel injected bike. they are easier to tune and diagnose. hope u find the prob.

 

Well I put the front forks as hard as they would go just to check, and the bike still "nose dives" a good inch or two just rolling it forward slightly and hitting the front brake. It is a little better, but not much. I can also (with modest effort) push the forks down on the full H setting. Is this typical, or should I feel more resistance?

For the last 2 days, I have had very little issue with the sputtering... I dont know if me wailing on the throttle the last week or so has helped clean it out or something, but that issue seems to be managable at the moment. I am still going to check hoses and all over the weekend if time allows.